Pressure differential  plug and method

ABSTRACT

A pressure differential plug including a mandrel, a baffle within the mandrel, and one or more passageways in the baffle, the passageways configured and dimensioned to restrict flow therethrough due to a valve coefficient thereof to both allow fluid flow therethrough and simultaneously allow the building of actuation pressure against the baffle without landing a member on the baffle. A borehole system including a borehole, a string in the borehole, the string including a plug as as in any prior embodiment. A method for causing an actuation via pressure including flowing fluid through a baffle of a plug as in any prior embodiment, increasing a flow rate through the baffle to raise pressure upstream of the baffle to an actuation level without seating a member on the baffle.

BACKGROUND

In the drilling and completion industry, there is often a need to runand set plugs in an open hole or a cased hole or even in a tubing stringfor the purpose of allowing an operator to apply pressure from surface.That pressure may be used for things such as setting other tools ortreating the formation including fracturing the formation. Using suchconfigurations is a two-step process. The plug (aka seat) is set in thedownhole environment and later a ball or similar is dropped to land onthe plug or seat thereby presenting a restriction to fluid flow suchthat pressure may be built against this combination of components. Thistype of configuration has worked extremely well in the industry for anextended period of time. The industry is however always open toimprovements in configurations and methods that enhance efficiency orreduce components and therefore cost.

SUMMARY

A pressure differential plug including a mandrel, a baffle within themandrel, and one or more passageways in the baffle, the passagewaysconfigured and dimensioned to restrict flow therethrough due to a valvecoefficient thereof to both allow fluid flow therethrough andsimultaneously allow the building of actuation pressure against thebaffle without landing a member on the baffle.

A borehole system including a borehole, a string in the borehole, thestring including a plug as as in any prior embodiment.

A method for causing an actuation via pressure including flowing fluidthrough a baffle of a plug as in any prior embodiment, increasing a flowrate through the baffle to raise pressure upstream of the baffle to anactuation level without seating a member on the baffle.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 is a longitudinal cross sectional view of a Pressure DifferentialPlug as described herein;

FIG. 2 is a side view of FIG. 1 in the direction of arrows 1-1 in FIG.1;

FIG. 3 is a transparent view of an alternate baffle having tortuouspassageways;

FIG. 4 is another view of a baffle plate with more passageways than thatshown in FIG. 2; and

FIG. 5 is an enlarged view of a portion of the baffle of FIG. 4illustrating sand particles bridging over the passageways.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

Referring to FIGS. 1 and 2 simultaneously, a Pressure Differential Plug10 is disclosed that allows for a pressure differential to be createdsufficient to take desired borehole actions based upon pressure withoutthe loss of the ability to flow fluid through the plug. The plug 10 isillustrated with a packer 12 but it is to be understood that thedisclosure hereof is directed to the inner portions of the tool suchthat providing tubing pressure cannot otherwise escape to an annulus 14,a packer would not be needed. In one embodiment, and as illustrated, theaction being taken by application of pressure to the tubing is to treatthe formation. In that case, the fluid inside the tubing willnecessarily be open to the annulus 14 and hence the packer would beneeded. The plug 10 includes a tubular mandrel 16 within which a baffle18 is disposed. The baffle may be secured in the mandrel 16 with threads17, screws, welding, adhesives, or be formed therein. The baffle 18 mayalso be a part of the mandrel 16 as in having been formed as a part ofthe mandrel 16. For example, the baffle 18 may be either subtractivelymachined or additively manufactured as a part of the mandrel 16.

The baffle 18, most easily identified in FIG. 2, includes a number ofpassageways 20 therein that range from 1 to any number of passagewaysthat are practically positionable in the area provided by the particularbaffle 16. For example, as illustrated there are 12 passageways 20. Itis to be appreciated that a larger number of passageways may be achievedby using smaller diameters of the passageways. While “diameter” is usedfor discussion purposes, there is no reason the passageways mustnecessarily be cylindrical but rather any tubular form may be employedas desired.

Important to the teaching herein is that in all embodiments hereofregardless of the number of passageways, size of passageways or shape ofpassageways, the passageways 20 collectively must restrict flowtherethrough due to a valve coefficient thereof to both allow fluid flowtherethrough and simultaneously allow the building of actuation pressureagainst the baffle without landing a member on the baffle. In anembodiment the actuation pressure is a formation fracture pressure andin another embodiment the actuation pressure is that pressure associatedwith the actuation of a downhole tool. In embodiments the passagewayscollectively must have a valve coefficient of less than 4.47. This canbe determined for a particular embodiment by using the equations:

Q _(gpm) =C _(v)*(ρ_(water) *ΔP/ρ)̂0.5 or rewritten as Q _(gpm) =C_(v)*(ΔP/SG)̂0.5 or rewritten as C _(v) =Q _(gpm)/(ρ_(water) *ΔP/ρ)̂0.5 orrewritten as C _(v) =Q _(gpm)/(ΔP/SG)̂0.5

Q_(gpm)=Flow Rate (gpm)

C_(v)=Valve Coefficient

ρ=Density (lb/ft³)

ρ_(water)=Water Density (lb/ft³)=62.4 lb/ft³

ΔP=Pressure Drop (psi)

SG=Specific gravity of the fluid

Maintaining configurations with a valve coefficient of less than 4.47provides for a condition where applied flow rate and pressure from thesurface will reach high enough levels in a target region to achieve theoperation desired, for example a fracturing job, all while maintaining aflowing fluid dynamic at the plug site (i.e. no member is seated on thebaffle). This allows for tools to be pumped to depth even with the plug10 in place, if desired. This avoids the difficulties of very earlyplugs that prevent all fluid flow once set and the difficulties of thosetraditional plugs that utilize a seat to preserve fluid flow when setbut require a ball drop (or similar member) to land on the seat toenable pressure up. And it will be appreciated by those of skill in theart that once the ball is seated, flow through is prevented and hencepumping other or additional tools to the site is not possible withoutremoving the ball.

As illustrated, plug 10 also includes standard anchoring equipment 22such as one or more slips 22 or other similar equipment.

In use, the plug 10 is installed in a tubular form which may be an openhole, a casing, a tubing, etc. and anchored there. A flow rate forflowing through the plug 10 may initially be established and thenincreased to a level where pressure is built against the baffle 18 andfracturing may occur. It will be understood that after setting of theplug 10, an operator may elect to run a set of guns to open the casingof tubing for access to the formation for a fracturing operation.

Further disclosed herein is a borehole system that includes a borehole24 within which a string 26 (casing, tubing, etc.) is positioned and thestring including a plug 10 as described above.

In an alternate embodiment, referring to FIG. 3, baffle 118 includespassageways 120 that are tortuous over their lengths. Tortuosity may beemployed to alter the valve coefficient of a baffle 118. While thetortuous path illustrated is a squared off path, it is to be understoodthat any tortuous path is acceptable such as a curved path, helicalpath, etc. as is desired to create the valve coefficient needed whileavoiding some other parameters that might otherwise be employed tosecure the desired valve coefficient.

In yet another embodiment, referring to FIGS. 4 and 5, a baffle 218 isillustrated with many passageways 220. In combination with the valvecoefficient as described above, it is also contemplated for thisembodiment that particles 240 such as sand or similar may be used tobridge over the individual passageways 220 further inhibiting fluid flowtherethrough.

Providing the velocity of fluid flow is sufficient to carry sandparticles, which is dictated by Stokes law, to wit:

w=2*(ρ_(p)'1ρ_(f))*g*r ²/(9*μ)

-   w=Particle settling velocity

ρ=fluid density (subscripts p and f indicate particle and fluidrespectively)

g=the acceleration due to gravity

r=the radius of the particle and

μ=the dynamic viscosity of the fluid,

then the particles 240 will be carried along in the fluid flow to thebaffle 218 and will bridge across the passageways 220 as seen in FIG. 5.

Set forth below are some embodiments of the foregoing disclosure:

Embodiment 1: A pressure differential plug including a mandrel, a bafflewithin the mandrel, and one or more passageways in the baffle, thepassageways configured and dimensioned to restrict flow therethrough dueto a valve coefficient thereof to both allow fluid flow therethrough andsimultaneously allow the building of actuation pressure against thebaffle without landing a member on the baffle.

Embodiment 2: The plug as in any prior embodiment wherein the one ormore passageways collectively present a valve coefficient of less than4.47.

Embodiment 3: The plug as in any prior embodiment wherein the plugfurther includes a packer and anchoring equipment.

Embodiment 4: The plug as in any prior embodiment wherein the baffle issecured in the mandrel with threads.

Embodiment 5: The plug as in any prior embodiment wherein the baffle isformed as a part of the mandrel.

Embodiment 6: The plug as in any prior embodiment wherein the one ormore passageways are cylindrical.

Embodiment 7: The plug as in any prior embodiment wherein the one ormore passageways are tortuous.

Embodiment 8: A borehole system including a borehole, a string in theborehole, the string including a plug as as in any prior embodiment.

Embodiment 9: A method for causing an actuation via pressure includingflowing fluid through a baffle of a plug as in any prior embodiment,increasing a flow rate through the baffle to raise pressure upstream ofthe baffle to an actuation level without seating a member on the baffle.

Embodiment 10: The method as in any prior embodiment further includingflowing particles to bridge over the one or more passageways in thebaffle.

Embodiment 11: The method as in any prior embodiment wherein theactuation is fracturing.

Embodiment 12: The method as in any prior embodiment wherein theactuation is of another tool.

Embodiment 13: The method as in any prior embodiment further includingreturning fluid flow to a level below pressure increase and flowingfluid through the baffle.

Embodiment 14: A method for making a pressure differential plug as inany prior embodiment wherein the baffle is subtractively machined in themandrel.

Embodiment 15: The method as in any prior embodiment wherein the baffleis additively manufactured with the mandrel.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Further, it should further be noted that the terms “first,”“second,” and the like herein do not denote any order, quantity, orimportance, but rather are used to distinguish one element from another.The modifier “about” used in connection with a quantity is inclusive ofthe stated value and has the meaning dictated by the context (e.g., itincludes the degree of error associated with measurement of theparticular quantity).

The teachings of the present disclosure may be used in a variety of welloperations. These operations may involve using one or more treatmentagents to treat a formation, the fluids resident in a formation, awellbore, and/or equipment in the wellbore, such as production tubing.The treatment agents may be in the form of liquids, gases, solids,semi-solids, and mixtures thereof. Illustrative treatment agentsinclude, but are not limited to, fracturing fluids, acids, steam, water,brine, anti-corrosion agents, cement, permeability modifiers, drillingmuds, emulsifiers, demulsifiers, tracers, flow improvers etc.Illustrative well operations include, but are not limited to, hydraulicfracturing, stimulation, tracer injection, cleaning, acidizing, steaminjection, water flooding, cementing, etc.

While the invention has been described with reference to an exemplaryembodiment or embodiments, it will be understood by those skilled in theart that various changes may be made and equivalents may be substitutedfor elements thereof without departing from the scope of the invention.In addition, many modifications may be made to adapt a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe claims. Also, in the drawings and the description, there have beendisclosed exemplary embodiments of the invention and, although specificterms may have been employed, they are unless otherwise stated used in ageneric and descriptive sense only and not for purposes of limitation,the scope of the invention therefore not being so limited.

What is claimed is:
 1. A pressure differential plug comprising: amandrel; a baffle within the mandrel; and one or more passageways in thebaffle, the passageways configured and dimensioned to restrict flowtherethrough due to a valve coefficient thereof to both allow fluid flowtherethrough and simultaneously allow the building of actuation pressureagainst the baffle without landing a member on the baffle.
 2. The plugas claimed in claim 1 wherein the one or more passageways collectivelypresent a valve coefficient of less than 4.47.
 3. The plug as claimed inclaim 1 wherein the plug further includes a packer and anchoringequipment.
 4. The plug as claimed in claim 1 wherein the baffle issecured in the mandrel with threads.
 5. The plug as claimed in claim 1wherein the baffle is formed as a part of the mandrel.
 6. The plug asclaimed in claim 1 wherein the one or more passageways are cylindrical.7. The plug as claimed in claim 1 wherein the one or more passagewaysare tortuous.
 8. A borehole system comprising: a borehole; a string inthe borehole, the string including a plug as claimed in claim
 1. 9. Amethod for causing an actuation via pressure comprising: flowing fluidthrough a baffle of a plug as claimed in claim 1; increasing a flow ratethrough the baffle to raise pressure upstream of the baffle to anactuation level without seating a member on the baffle.
 10. The methodas claimed in claim 9 further including flowing particles to bridge overthe one or more passageways in the baffle.
 11. The method as claimed inclaim 9 wherein the actuation is fracturing.
 12. The method as claimedin claim 9 wherein the actuation is of another tool.
 13. The method asclaimed in claim 9 further including returning fluid flow to a levelbelow pressure increase and flowing fluid through the baffle.
 14. Amethod for making a pressure differential plug as claimed in claim 1wherein the baffle is subtractively machined in the mandrel.
 15. Themethod as claimed in claim 14 wherein the baffle is additivelymanufactured with the mandrel.